12 Coins Puzzle

There are 12 coins, all identical in appearance, and all identical in weight except for one, which is either heavier or lighter than the remaining 11 coins. Determine which is the counterfeit coin, and whether it is lighter or heavier than the real coins, in only 3 weightings with a balance scale.

The simulation below can be used to help you solve this puzzle. A random coin will be selected as the counterfeit.

Use the table below to place the selected coins on the appropriate side of the balance, and
then click the 'Weigh' button. You can use the balance scales 3 times.